Method of Processing Tailings from Solvent-Based Hydrocarbon Extraction

ABSTRACT

Described is a method of processing a bituminous feed. The bituminous feed is solvent extracted to form a bitumen-rich stream and a bitumen-lean stream. Solvent is recovered from the bitumen-rich stream to form a bitumen product. Solvent and water are recovered from the bitumen-lean stream to form dry tailings with a moisture content of less than 40 wt.%. The dry tailings are separated into at least two streams, each stream having a moisture content of less than 40 wt. %, based on at least one physical or chemical property. At least one of the at least two streams is then used at an oil sands mine site. In this way, the dry tailings may be used more effectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Canadian PatentApplication 2,753,811 filed Sep. 29, 2011 entitled METHOD OF PROCESSINGTAILINGS FROM SOLVENT-BASED HYDROCARBON EXTRACTION, the entirety ofwhich is incorporated by reference herein.

FIELD

The present disclosure relates generally to the field of hydrocarbonextraction from mineable deposits, such as bitumen from oil sands. Moreparticularly, the present disclosure relates to the processing oftailings from solvent-based hydrocarbon extraction.

BACKGROUND

Oil sands are sand deposits which, in addition to sand, comprise clays,connate water, and bitumen. Depending on the geographic location,bitumen may be recovered by mining and extraction methods or by in-siturecovery methods.

Oil sands ore in a mining and extraction operation is typicallyprocessed using mechanical and chemical techniques to separate thebitumen from the sands. In general, water-based extraction andsolvent-based extraction are the two processes that have been proposedor used to extract bitumen from mined oil sands. In the case ofwater-based extraction, water is the dominant liquid in the process andthe extraction occurs by having water displace the bitumen on thesurface of the solids. In the case of solvent-based extraction, thesolvent is the dominant liquid and the extraction of the bitumen occursby dissolving bitumen into the solvent.

The commercial application of a solvent-based extraction process has,for various reasons, eluded the oil sands industry. A major challenge tothe application of solvent-based extraction to oil sands is the tendencyof fine particles within the oil sands to hamper the separation ofsolids from the bitumen extract. Solvent extraction with solidsagglomeration is a technique that has been proposed to deal with thischallenge. The original application of this technology was coinedSolvent Extraction Spherical Agglomeration (SESA). A more recentdescription of the SESA process can be found in

Previously described methodologies for SESA have not been commerciallyadopted. In general, the SESA process involves mixing oil sands with ahydrocarbon solvent, adding a bridging liquid to the oil sands slurry,agitating the mixture in a slow and controlled manner to nucleateparticles, and continuing such agitation to permit these nucleatedparticles to form larger multi-particle spherical agglomerates forremoval. The bridging liquid is preferably water or an aqueous solutionsince the solids of oil sands are mostly hydrophilic and water isimmiscible with hydrocarbon solvents. It has been found that thebridging liquid used in the process can be water with both a high finesand salt content. In fact, in certain embodiments of the SESA process,it may be preferable to have aqueous bridging liquid with either highfines content and/or high dissolved solid content.

The SESA process described by Meadus et al. in U.S. Pat. No. 4,057,486,involves combining solvent extraction with solids agglomeration toachieve dry tailings suitable for direct mine refill. In the process,organic material is separated from oil sands by mixing the oil sandsmaterial with an organic solvent to form a slurry, after which anaqueous bridging liquid is added in the amount of 8 to 50 wt % of thefeed mixture. By using controlled agitation, solid particles from oilsands come into contact with the aqueous bridging liquid and adhere toeach other to form macro-agglomerates of a mean diameter of 2 mm orgreater. The formed agglomerates are more easily separated from theorganic extract compared to un-agglomerated solids. The organic extractfree agglomerates can be sintered at high temperatures to make usefulconstruction material. For example, halide salts such as NaCl, KCl, andCaCl₂ can be dissolved in the aqueous bridging liquid to formagglomerates that, when sintered at elevated temperatures, produce verystrong aggregates.

The oil sands industry has become relatively adept at handling aqueoustailings streams from water-based bitumen extraction. These tailings aresorted by size in a variety of operations, and bitumen and minerals canthen be extracted. For instance, settlers and cyclones are currentlyused for aqueous tailings to separate particular streams by particlesize distribution; the coarser fraction can be pumped into place andrapidly drained, making it an excellent construction material.

Oil sands tailings are unique among mining tailings in that theycomprise residual hydrocarbons. They often also comprise metals, clays,and sands. In a water-based extraction process, oil sand tailingscomprise water. Because of this water content, the tailings are pumpableand easily fed into separation units common in the oil industry. In thisway, metals can be extracted from the aqueous tailings, bitumen can beskimmed from floating mats on tailings ponds, and coarse and finesfractions can be separated by gravity or enhanced gravity separation Allof these separations of aqueous tailings currently take place in the oilsands industry.

While one solution to treating solid tailings could be to wet thetailings and subject them to the same processes as aqueous tailings thissolution greatly diminishes the value of a process that produces drytailings in the first place.

Outside of the oil sands mining industry, solids handling and separationis common in the mining industry. In particular, several mechanismsexist for the dry beneficiation of coal, as described by Lockhart, “DryBeneficiation of Coal”, Powder Technology 40 (1984) 17-42 and also byDwari and Rao, “Dry Beneficiation of Coal—A Review”, Mineral Processingand Extractive Metallurgy Review 28 (2007) 177-234. These techniques areapplied to ores, which are routinely separated and classified, and themethods listed above, such as cyclones, sieves, magnets, etc., areestablished technologies.

B. D. Sparks and F. W. Meadus, “A Combined Solvent Extraction andAgglomeration Technique for the Recovery of Bitumen from Tar Sands”,Canadian Chemical Engineering Conference, Calgary: Energy Processing:Tar Sands Technology, 1979 describes the production of solidagglomerates, and refers to the storage of these materials withoutcontainment.

U.S. Patent Publication No. 2010/0258478 Moran et al. describes a methodfor separating aqueous oil sand tailings into a bitumen rich stream anda dry mineral stream, but separation of the dry mineral stream is notmentioned.

Newman and Arnold, in “Dry stack tailings design for the Rosemont Copperproject”, Proceedings of the 14th International Conference on Tailingsand Mine Waste 2010, Vail, Colo., describe a dry tailings projectrequiring a buttress and a cover requirement for the tailings facility.

Lupo and Hall, in “Dry stack tailings—design considerations”, ibid,describe that tailings could be distributed in a stack based on theirmoisture content exiting the extraction process to reduce flow of fluidtailings and dyke strength requirements. No separation is mentioned;instead, drier tailings resulting from the primary process are depositedin one way while process upset tailings are deposited in another.

U.S. Pat. No. 4,240,897 (Clarke) describes a method of producing drytailings and recommends that these tailings be mixed with overburden andused as backfill for reclamation. No separation of tailings ismentioned.

U.S. Pat. No. 7,695,612 (Erasmus) describes a method of recovering heavyminerals from aqueous oil sands tailings.

SUMMARY

Described is a method of processing a bituminous feed. The bituminousfeed is solvent extracted to form a bitumen-rich stream and abitumen-lean stream. Solvent is recovered from the bitumen-rich streamto form a bitumen product. Solvent and water are recovered from thebitumen-lean stream to form dry tailings with a moisture content of lessthan 40 wt. %. The dry tailings are separated into at least two streams,each stream having a moisture content of less than 40 wt. %, based on atleast one physical or chemical property. At least one of the at leasttwo streams is then used at an oil sands mine site. In this way, the drytailings may be used more effectively.

Other aspects and features of the present disclosure will becomeapparent to those ordinarily skilled in the art upon review of thefollowing description of specific embodiments in conjunction with theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way ofexample only, with reference to the attached figures.

FIG. 1 is a schematic illustrating a disclosed embodiment.

FIG. 2 is a schematic illustrating a disclosed embodiment.

FIG. 3 is a schematic illustrating a disclosed embodiment.

FIG. 4 is a schematic illustrating a disclosed embodiment.

DETAILED DESCRIPTION

As used herein, the term “bituminous feed” refers to a stream derivedfrom oil sands that requires downstream processing in order to realizevaluable bitumen products or fractions. The bituminous feed is one thatcomprises bitumen along with undesirable components. Such a bituminousfeed may be derived directly from oil sands, and may be, for example,raw oil sands ore. Further, the bituminous feed may be a feed that hasalready realized some initial processing but nevertheless requiresfurther processing. Also, recycled streams that comprise bitumen incombination with other components for removal as described herein can beincluded in the bituminous feed. A bituminous feed need not be deriveddirectly from oil sands, but may arise from other processes. Forexample, a waste product from other extraction processes which comprisesbitumen that would otherwise not have been recovered may be used as abituminous feed. Such a bituminous feed may be also derived directlyfrom oil shale oil, bearing diatomite or oil saturated sandstones.

As used herein, the term “agglomerate” refers to conditions that producea cluster, aggregate, collection or mass, such as nucleation,coalescence, layering, sticking, clumping, fusing and sintering, asexamples.

As used herein, the term “dry tailings” refers to tailings with amoisture content of less than 40 wt. %.

Dry tailings are not common in the oil sands industry. Where produced,dry oil sands tailings have been seen as an end state rather than as acomposition suitable for further processing and use. Additionally,solid-solid separation is not common in the oil sands industry. Asdescribed herein, dry tailings from solvent-based extraction may beprocessed for advantageous use.

As described in the summary section, the present disclosure relates to amethod of processing a bituminous feed. The bituminous feed is solventextracted to form a bitumen-rich stream and a bitumen-lean stream.Solvent is recovered from the bitumen-rich stream to form a bitumenproduct. Solvent and water are recovered from the bitumen-lean stream toform dry tailings with a moisture content of less than 40 wt. %. The drytailings are separated into at least two streams, each stream having amoisture content of less than 40 wt. %, based on at least one physicalor chemical property. At least one of the at least two streams is thenused at an oil sands mine site.

Suitable solvent-based extraction processes may include solvent-basedextraction processes that uses an aqueous stream in the extractionprocess. Exemplary solvent-based extraction processes include, but arenot limited to, those described in the background section, thosedescribed below, and those described in Canadian Patent ApplicationSerial No. 2,724,806 (“Adeyinka et al.”) filed Dec. 10, 2010 andentitled “Process and Systems for Solvent Extraction of Bitumen from OilSands”.

Summary of Processes of Solvent Extraction Described in Adeyinka et al.

One method of extracting bitumen from oil sands in a manner that employssolvent extraction with solids agglomeration is described by Adeyinka etal. In this process, a solvent is combined with a bituminous feedderived from oil sands to form an initial slurry. Separation of theinitial slurry into a fine solids stream and a coarse solids stream maybe followed by mixing a bridging liquid with the fine solid stream andagglomeration of solids from the fine solids stream to form anagglomerated slurry. The agglomerated slurry can be separated intoagglomerates and a low solids bitumen extract. Optionally, the coarsesolids stream may be reintroduced and further extracted in theagglomerated slurry. A low solids bitumen extract can be separated fromthe agglomerated slurry for further processing. Optionally, the mixingof a second solvent with the low solids bitumen extract to extractbitumen may take place, forming a solvent-bitumen low solids mixture,which can then be separated further into low grade and high gradebitumen extracts. Recovery of solvent from the low grade and/or highgrade extracts is conducted, to produce bitumen products of commercialvalue. The agglomerates may be sent to a tailings solvent recovery unitto recover solvent and water, leaving dry tailings. Additional detailsof a solvent-based extraction process are described below.

Processing of Tailings from Solvent-Based Extraction

Dry tailings from solvent-based bitumen extraction may be separated intoat least two streams, each stream having a moisture content of less than40 wt. %. These streams may be suitable for different uses. At least onestream may be suitable for use at the oil sands mine site, or anotheroil sands mine site, including an water-based bitumen extraction minesite. The separation is effected by leveraging a physical or chemicalproperty of the tailings.

Characteristics to be leveraged for the dry oil sands tailingsseparation may include, but are not limited to size, density, dipolemoment, permeability, shape, magnetism, adhesiveness, wettability,attrition, strength, solubility, inductiveness, and electric charge.

Suitable methods or devices for separating dry oil sands tailings mayinclude, but are not limited to a screen, a sieve, a blower (forinstance an air blower), gravity separation or enhanced gravityseparation (for instance using a cyclone, centrifuge, or settler),filtration, electrostatic precipitation, a magnet, a shaker, a grinder,milling, and rolling.

Separation may also be achieved naturally without using a device, i.e.by consolidation over time. In one embodiment, the dry tailings arerolled down an incline such as a hill or mine face. The tailingsseparate themselves according to size and/or density. Materials at thetop are of a lighter density and/or a smaller size. In anotherembodiment, first and second streams are separated from one another by asieve, screen, or a blower. In another embodiment, the tailings areseparated in a cyclone. In another embodiment, they are separatedaccording to their electrostatic charge. In another embodiment, they areseparated by a magnetic field. In another embodiment, the tailings areseparated by their tendency to cling to a surface. In anotherembodiment, the tailings are separated by their strength. In anotherembodiment, the tailings are separated by being selectively crushed in amill.

A first of the separated streams may be used as a construction materialwhile a second is used for mine backfill. In this embodiment, the firststream may be a coarser stream. The second stream may be comprised of afiner fraction of particles. The separation into these streams wouldallow the coarser stream to be mixed with water because it would rapidlydrain. The coarser material could subsequently be pumped into place,allowing construction according to the general practice in the industry,for instance for construction of a mine form at the oil sands site, suchas a dyke or a road.

At least one of the at least two streams may be used drainage, asfoundation, as a road, for reclamation, or as a dyke, at the oil sandsmine site, or is used in a deposit for growing vegetation.

A stream of finer particle sized tailings may be separated from a streamof coarser particle sized tailings. The finer particles are used in thelining of a tailings cell to reduce its permeability to water. Thetailings could be placed at the bottom of, along the walls of, and/or onthe cap of a tailings deposit.

The streams may be separated by charge or magnetism. An incomingtailings stream is subjected to a magnetic moment or an electrostaticcharge. The portion of the incoming tailings stream that responds tothis force is captured separately from the portion that does not respondto the force. The mineral composition of the tailings being different,one of the tailings streams, rich in one or more minerals, is used in amineral extraction process to recover the valuable minerals. Anotherstream is used for mine backfill. In another embodiment, the mineralpoor stream is placed in a deposit closer to potential contact withwater. The mineral rich tailings are placed farther away from potentialcontact with water. In another embodiment, the mineral rich stream isplaced under water, and the mineral poor stream is placed in or over thewater table.

The separation may be used to produce streams of differing sizes ordensities, which can be used in different capacities in mine backfill.The lighter stream may be more prone to dusting, and may be covered withanother material, such as a coarser stream of tailings. The heavierstream may be used as a capillary barrier. In this application, thecoarser stream has a low hydraulic wicking potential while dry ascompared to the finer stream. A material may be selectively moved fromthe deposit based on its materials properties.

The tailings may be separated into streams that differ by their chemicalcomposition into a chemically active stream and a chemically inertstream. The tailings may be separated into a stream that can be heattreated to form a cementitious material. The tailings may be separatedinto a stream that can be mixed with a chemical binder and anotherstream that is not mixed with a chemical binder.

As described above, the term “dry tailings” refers to tailings with amoisture content of less than 40 wt. %. In another embodiment, the drytailings may have a moisture content of less than 30 wt. %.

FIG. 1 illustrates an embodiment using airblowing to separate drytailings cyclonically. Tailings 100 may be dried 101 to form drytailings 102. The dry tailings 102 are airblown in a cyclone 104 forseparation by particle size and/or density. The cyclone produces alighter stream 106 and a heavier stream 108. The lighter stream 106 maycomprise mainly clays and may be suitable as an impermeable layer, suchas a clay liner.

The heavier stream 108 may be a coarser material and may be suitable foruse as a construction material, such as for roads or containment. In anexample where both streams are used at the mine site, as illustrated inFIG. 1, the heavier stream 108 may be used as a containment structure110 and the lighter stream 108 may be used as an impermeable layer 112,for containing aqueous tailings 114.

FIG. 2 illustrates an embodiment leveraging the magnetic dipole momentpresent in some of the dry tailings. Tailings 200 may be dried 201 toform dry tailings 202. The dry tailings 202 are separated using a magnet204 into a higher dipole moment containing stream 206 which may have ahigher concentration of metals, and a lower dipole moment containingstream 208. The higher dipole moment containing stream 206 may befurther processed to reclaim metals. The lower dipole moment containingstream 208 may be used as mine backfill.

FIG. 3 illustrates an embodiment where dry tailings 302 are passed to ablower 304 to separate the dry tailings 302 according to how prone theyare to being carried by the wind. The coarser fraction 306 drops outfaster than the finer fraction 308. The coarser fraction 306 may bedeposited in a windy area, or on a higher elevation than the finerfraction 308. Alternatively, the finer fraction 308 may be placed firstand then covered by the coarser fraction 306 to reduce dusting.

FIG. 4 illustrates an embodiment where an induced dipole moment 404separates dry tailings 402 according to the availability of mineralscontaining a dipole moment. The tailings 400 and dryer 401 are alsoillustrated. The material containing a higher dipole moment 406 is moreprone to acid rock drainage and may be placed in a subaqueousenvironment to mitigate its oxidation. This layer may be covered withthe material containing a lower dipole moment 408. Alternatively, thematerial containing a higher dipole moment 406 may be placed away froman aqueous material 410, and is insulated with the material containing alower dipole moment 408. The mine pit 412 is also illustrated.

For dry sands tailings, many uses may favor a particular fraction of thetailings rather than the whole tailings. Furthermore, some fractions ofthe tailings may be preferred over other fractions of the tailings.Examples include construction materials for dykes or roads, as backfillwithin the mine, or as a recycle stream to aid in extraction. An exampleof a recycle stream aiding in the extraction process is as follows. Ithas been previously shown that increasing the solids content, or morepreferably the fines content, of a slurry may improve the solventextraction with solids agglomeration process. Thus, a fines solidsstream produced by a process described herein may be redirected back tothe solvent extraction process to aid in solids agglomeration. More usescan be envisioned, such as mineral extraction from a mineral richstream, as a pH buffer in a tailings pond, or as an absorption stream toenhance the solids content of fluid tailings, as described above. Oneexample is to use the fines streams as an impermeable layer. Such animpermeable layer can be used as liner for mature fine tailings producedin an aqueous-based extraction process.

The moisture content of the tailings may be reduced prior to separation,for instance by drying, extraction, or agglomeration.

At least one of the at least two streams may be mixed with an additivecomprising a polymer, gypsum, alum, or a resin.

At least one of the at least two streams may be mixed with tailingsgenerated from an aqueous-based bitumen extraction process.

At least one of the at least two streams may be grinded.

One or more heavy metals may be recovered from at least one of the atleast two streams. The heavy metals may be titanium, strontium, orvanadium, or a combination thereof.

At least one of the at least two streams may be recycled into thesolvent extraction of step a).

The dry tailings may have a water:solids mass ratio of less than 0.15:1.

The oil sands mine site may be mine site employing aqueous-based bitumenextraction or a mine site employing solvent-based bitumen extraction.

Description of one Solvent-Based Extraction Process Using Agglomeration:Agglomeration.

In one embodiment, the formed agglomerates are sized on the order of0.1-1.0 mm, or on the order of 0.1-0.3 mm. In one embodiment, at least80 wt. % of the formed agglomerates are 0.1-1.0 mm, or 0.1 to 0.3 mm insize. The rate of agglomeration may be controlled by a balance betweenintensity of agitation within the agglomeration vessel, shear within thevessel which can be adjusted by for example changing the shape or sizeof the vessel, fines content of the slurry, bridging liquid addition,and residence time of the agglomeration process. The agglomerated slurrymay have a solids content of 20 to 70 wt %.

Agitation.

Agglomeration is assisted by some form of agitation. The form ofagitation may be mixing, shaking, rolling, or another known suitablemethod. The agitation of the feed need only be severe enough and ofsufficient duration to intimately contact the emulsion with the solidsin the feed. Exemplary rolling type vessels include rod mills andtumblers. Exemplary mixing type vessels include mixing tanks, blenders,and attrition scrubbers. In the case of mixing type vessels, asufficient amount of agitation is needed to keep the formed agglomeratesin suspension. In rolling type vessels, the solids content of the feedis, in one embodiment, greater than 40 wt. % so that compaction forcesassist agglomerate formation. The agitation of the slurry has an impacton the growth of the agglomerates. In the case of mixing type vessels,the mixing power can be increased in order to limit the growth ofagglomerates by attrition of said agglomerates. In the case of rollingtype vessels the fill volume and rotation rate of the vessel can beadjusted in order to increase the compaction forces used in thecomminution of agglomerates. These agitation parameters can be adjustedin the control system described herein.

Extraction Liquor.

The extraction liquor comprises a solvent used to extract bitumen fromthe bituminous feed. The term “solvent” as used herein should beunderstood to mean either a single solvent, or a combination ofsolvents.

In one embodiment, the extraction liquor comprises a hydrocarbon solventcapable of dissolving the bitumen. The extraction liquor may be asolution of a hydrocarbon solvent(s) and bitumen, where the bitumencontent of the extraction liquor may range between 10 and 70 wt %, or 10and 50 wt %. It may be desirable to have dissolved bitumen within theextraction liquor in order to increase the volume of the extractionliquor without an increase in the required inventory of hydrocarbonsolvent(s). In cases where non-aromatic hydrocarbon solvents are used,the dissolved bitumen within the extraction liquor also increases thesolubility of the extraction liquor towards dissolving additionalbitumen.

The extraction liquor may be mixed with the bituminous feed to form aslurry where most or all of the bitumen from the oil sands is dissolvedinto the extraction liquor. In one embodiment, the solids content of theslurry is in the range of 10 wt % to 75 wt %, or 50 to 65 wt %. A slurrywith a higher solids content may be more suitable for agglomeration in arolling type vessel, where the compressive forces aid in the formationof compact agglomerates. For turbulent flow type vessels, such as anattrition scrubber, a slurry with a lower solids content may be moresuitable.

The solvent used in the process may include low boiling point solventssuch as low boiling point cycloalkanes, or a mixture of suchcycloalkanes, which substantially dissolve asphaltenes. The solvent maycomprise a paraffinic solvent in which the solvent to bitumen ratio ismaintained at a level to avoid or limit precipitation of asphaltenes.

While it is not necessary to use a low boiling point solvent, when it isused, there is the extra advantage that solvent recovery through anevaporative process proceeds at lower temperatures, and requires a lowerenergy consumption. When a low boiling point solvent is selected, it maybe one having a boiling point of less than 100° C.

The solvent selected according to certain embodiments may comprise anorganic solvent or a mixture of organic solvents. For example, thesolvent may comprise a paraffinic solvent, an open chain aliphatichydrocarbon, a cyclic aliphatic hydrocarbon, or a mixture thereof.Should a paraffinic solvent be utilized, it may comprise an alkane, anatural gas condensate, a distillate from a fractionation unit (ordiluent cut), or a combination of these containing more than 40% smallchain paraffins of 5 to 10 carbon atoms. These embodiments would beconsidered primarily a small chain (or short chain) paraffin mixture.Should an alkane be selected as the solvent, the alkane may comprise anormal alkane, an iso-alkane, or a combination thereof. The alkane mayspecifically comprise heptane, iso-heptane, hexane, iso-hexane, pentane,iso-pentane, or a combination thereof. Should a cyclic aliphatichydrocarbon be selected as the solvent, it may comprise a cycloalkane of4 to 9 carbon atoms. A mixture of C₄-C₉ cyclic and/or open chainaliphatic solvents would be appropriate.

Exemplary cycloalkanes include cyclohexane, cyclopentane, or a mixturethereof.

If the solvent is selected as the distillate from a fractionation unit,it may for example be one having a final boiling point of less than 180°C. An exemplary upper limit of the final boiling point of the distillatemay be less than 100° C.

A mixture of C₄-C₁₀ cyclic and/or open chain aliphatic solvents wouldalso be appropriate. For example, it can be a mixture of C₄-C₉ cyclicaliphatic hydrocarbons and paraffinic solvents where the percentage ofthe cyclic aliphatic hydrocarbons in the mixture is greater than 50%.

Extraction liquor may be recycled from a downstream step. For instance,as described below, solvent recovered in a solvent recovery unit, may beused to wash agglomerates, and the resulting stream may be used asextraction liquor. As a result, the extraction liquor may compriseresidual bitumen and residual solid fines. The residual bitumenincreases the volume of the extraction liquor and it may increase thesolubility of the extraction liquor for additional bitumen dissolution.

The solvent may also include additives. These additives may or may notbe considered a solvent per se. Possible additives may be componentssuch as de-emulsifying agents or solids aggregating agents. Having anagglomerating agent additive present in the bridging liquid anddispersed in the first solvent may be helpful in the subsequentagglomeration step. Exemplary agglomerating agent additives includecements, fly ash, gypsum, lime, brine, water softening wastes (e.g.magnesium oxide and calcium carbonate), solids conditioning andanti-erosion aids such as polyvinyl acetate emulsion, commercialfertilizer, humic substances (e.g. fulvic acid), polyacrylamide basedflocculants and others. Additives may also be added prior to gravityseparation with the second solvent to enhance removal of suspendedsolids and prevent emulsification of the two solvents. Exemplaryadditives include methanoic acid, ethylcellulose and polyoxyalkylateblock polymers.

Bridging Liquid.

A bridging liquid is a liquid with affinity for the solids particles inthe bituminous feed, and which is immiscible in the solvent. Exemplaryaqueous liquids may be recycled water from other aspects or steps of oilsands processing. The aqueous liquid need not be pure water, and mayindeed be water containing one or more salt, a waste product fromconventional aqueous oil sand extraction processes which may includeadditives, aqueous solutions with a range of pH, or any other acceptableaqueous solution capable of adhering to solid particles within anagglomerator in such a way that permits fines to adhere to each other.An exemplary bridging liquid is water.

The total amount of bridging liquid added to the slurry may becontrolled in order to optimize bitumen recovery and the rate ofsolid-liquid separation. By way of examples, the total amount ofbridging liquid added to the slurry may be such that a ratio of bridgingliquid plus connate water from the bituminous feed to solids within theagglomerated slurry is in the range of 0.02 to 0.25, or in the range of0.05 to 0.11.

The bridging liquid may be added in a concentration of less than 50 wt %of the oil sands feed, or less 25 wt %.

In one embodiment, the bridging liquid may comprise fine particles(sized less than 44 pm) suspended therein. These fine particles mayserve as seed particles for the agglomeration process. In oneembodiment, the bridging liquid has a solids content of less than 40 wt.%.

Ratio of Solvent to Bitumen for Agglomeration.

The process may be adjusted to render the ratio of the solvent tobitumen in the agglomerator at a level that avoids precipitation ofasphaltenes during agglomeration. Some amount of asphalteneprecipitation is unavoidable, but by adjusting the amount of solventflowing into the system, with respect to the expected amount of bitumenin the bituminous feed, when taken together with the amount of bitumenthat may be entrained in the extraction liquor used, can permit thecontrol of a ratio of solvent to bitumen in the agglomerator. When thesolvent is assessed for an optimal ratio of solvent to bitumen duringagglomeration, the precipitation of asphaltenes can be minimized oravoided beyond an unavoidable amount. Another advantage of selecting anoptimal solvent to bitumen ratio is that when the ratio of solvent tobitumen is too high, costs of the process may be increased due toincreased solvent requirements.

An exemplary ratio of solvent to bitumen to be selected as a targetratio during agglomeration is less than 2:1. A ratio of 1.5:1 or less,and a ratio of 1:1 or less, for example, a ratio of 0.75:1, would alsobe considered acceptable target ratios for agglomeration. For clarity,ratios may be expressed herein using a colon between two values, such as“2:1”, or may equally be expressed as a single number, such as “2”,which carries the assumption that the denominator of the ratio is 1 andis expressed on a weight to weight basis.

Measurement of the solvent and bitumen content of the extraction liquorand/or bitumen extract could occur directly or by proxy. Directmeasurement of solvent and bitumen content could involve evaporating offthe solvent and measuring the mass of both liquids, or use of a gaschromatograph, mass balance, spectrometer, or titration. Indirectmeasurement of solvent and bitumen content could include measuring :density, the index of refraction, opacity, or other properties.

Slurry System.

The slurry system may optionally be a mix box, a pump, or a combinationof these. By slurrying the extraction liquor together with thebituminous feed, and optionally with additional additives, the bitumenentrained within the feed is given an opportunity to become extractedinto the solvent phase prior to agglomeration within the agglomerator.

The resulting slurry from the slurry system may have a solid content inthe range of 20 to 65 wt %. In another embodiment, the slurry may have asolid content in the range of 20 to 50 wt %. In another embodiment, theslurry may have a solid content in the range of 40 to 65 wt %. In thecase of mixing type vessels, a lower solid content may be preferredsince that will assist in the proper mixing of the bridging liquid andreduce the mixing energy needed to keep the slurry well mixed. In thecase of rolling type vessels, a higher solid content may be preferredsince that will increase the compaction forces used in the comminutionof agglomerates. Additionally, the increased compaction forces mayreduce the amount of hydrocarbons that remain in the agglomerates andproduce stronger agglomerates.

The preferred temperature of the slurry is in the range of 20-60° C. Anelevated slurry temperature is desired in order to increase the bitumendissolution rate and reduce the viscosity of the slurry to promote moreeffective sand digestion and agglomerate formation. Temperatures above60° C. are generally avoided due to the complications resulting fromhigh vapor pressures.

Residence Time.

The residence time of the extraction process may be greater than 5minutes, or may be greater than 10 minutes, or may be greater than 15minutes, or may greater than 30 minutes. Depending on the desired levelof agglomeration, the residence time of the agglomeration process may bein the range of 15 seconds to 10 minutes. In order to maximize bitumenrecovery, the residence time of the agglomeration process may be in therange of 1 to 5 minutes.

Solid-Liquid Separator.

As described above, the agglomerated slurry may be separated into a lowsolids bitumen extract and agglomerates in a solid-liquid separator. Thesolid-liquid separator may comprise any type of unit capable ofseparating solids from liquids, so as to remove agglomerates. Exemplarytypes of units include a gravity separator, a clarifier, a cyclone, ascreen, a belt filter or a combination thereof.

The system may contain a solid-liquid separator but may alternativelycontain more than one. When more than one solid-liquid separation stepis employed at this stage of the process, it may be said that both stepsare conducted within one solid-liquid separator, or if such steps aredissimilar, or not proximal to each other, it may be said that a primarysolid-liquid separator is employed together with a secondarysolid-liquid separator. When a primary and secondary unit are bothemployed, generally, the primary unit separates agglomerates, while thesecondary unit involves washing agglomerates.

Non-limiting methods of solid-liquid separation of an agglomeratedslurry are described in Canadian Patent Application Serial No. 2,724,806(Adeyinka et al.), filed Dec. 10, 2010.

Secondary Stage of Solid-Liquid Separation to Wash Agglomerates.

As a component of the solid-liquid separator, a secondary stage ofseparation may be introduced for countercurrently washing theagglomerates separated from the agglomerated slurry. The initialseparation of agglomerates may be said to occur in a primarysolid-liquid separator, while the secondary stage may occur within theprimary unit, or may be conducted completely separately in a secondarysolid-liquid separator. By “countercurrently washing”, it is meant thata progressively cleaner solvent is used to wash bitumen from theagglomerates. Solvent involved in the final wash of agglomerates may bere-used for one or more upstream washes of agglomerates, so that themore bitumen entrained on the agglomerates, the less clean will be thesolvent used to wash agglomerates at that stage. The result being thatthe cleanest wash of agglomerates is conducted using the cleanestsolvent.

A secondary solid-liquid separator for countercurrently washingagglomerates may be included in the system or may be included as acomponent of a system described herein. The secondary solid-liquidseparator may be separate or incorporated within the primarysolid-liquid separator. The secondary solid-liquid separator mayoptionally be a gravity separator, a cyclone, a screen or belt filter.Further, a secondary solvent recovery unit for recovering solventarising from the solid-liquid separator can be included. The secondarysolvent recovery unit may be a conventional fractionation tower or adistillation unit.

When conducted in the process, the secondary stage for countercurrentlywashing the agglomerates may comprise a gravity separator, a cyclone, ascreen, a belt filter, or a combination thereof.

The solvent used for washing the agglomerates may be solvent recoveredfrom the low solids bitumen extract, as described in Canadian PatentApplication Serial No. 2,724,806 (Adeyinka et al.). A second solvent mayalternatively or additionally be used as described in Canadian PatentApplication Serial No. 2,724,806 (Adeyinka et al.) for additionalbitumen extraction downstream of the agglomerator.

Recycle and Recovery of Solvent.

The process may involve removal and recovery of solvent used in theprocess.

In this way, solvent is used and re-used, even when a good deal ofbitumen is entrained therein. Because an exemplary solvent:bitumen ratioin the agglomerator may be 2:1 or lower, it is acceptable to userecycled solvent containing bitumen to achieve this ratio. The amount ofmake-up solvent required for the process may depend solely on solventlosses, as there is no requirement to store and/or not re-use solventthat has been used in a previous extraction step. When solvent is saidto be “removed”, or “recovered”, this does not require removal orrecovery of all solvent, as it is understood that some solvent will beretained with the bitumen even when the majority of the solvent isremoved.

The system may contain a single solvent recovery unit for recovering thesolvent(s) arising from the gravity separator. The system mayalternatively contain more than one solvent recovery unit.

Solvent may be recovered by conventional means. For example, typicalsolvent recovery units may comprise a fractionation tower or adistillation unit. The solvent recovered in this fashion will notcontain bitumen entrained therein. This clean solvent is preferably usedin the last wash stage of the agglomerate washing process in order thatthe cleanest wash of the agglomerates is conducted using the cleanestsolvent.

The solvent recovered in the process may comprise entrained bitumentherein, and can thus be re-used as the extraction liquor for combiningwith the bituminous feed. Other optional steps of the process mayincorporate the solvent having bitumen entrained therein, for example incountercurrent washing of agglomerates, or for adjusting the solvent andbitumen content prior to agglomeration to achieve the selected ratiowithin the agglomerator that avoids precipitation of asphaltenes.

The agglomerates may be sent to a tailings solvent recovery unit torecover solvent and water, leaving dry tailings.

Dilution of Agglomerator Discharge to Improve Product Quality.

Solvent may be added to the agglomerated slurry for dilution of theslurry before discharge into the primary solid-liquid separator, whichmay be for example a deep cone settler. This dilution can be carried outin a staged manner to pre-condition the primary solid-liquid separatorfeed to promote higher solids settling rates and lower solids content inthe solid-liquid separator's overflow. The solvent with which the slurryis diluted may be derived from recycled liquids from the liquid-solidseparation stage or from other sources within the process.

When dilution of agglomerator discharge is employed in this embodiment,the solvent to bitumen ratio of the feed into the agglomerator is set toobtain from about 10 to about 90 wt % bitumen in the discharge, and aworkable viscosity at a given temperature. In certain cases, theseviscosities may not be optimal for the solid-liquid separation (orsettling) step. In such an instance, a dilution solvent of equal orlower viscosity may be added to enhance the separation of theagglomerated solids in the clarifier, while improving the quality of theclarifier overflow by reducing viscosity to permit more solids tosettle. Thus, dilution of agglomerator discharge may involve adding thesolvent, or a separate dilution solvent, which may, for example,comprise an alkane.

In the preceding description, for purposes of explanation, numerousdetails are set forth in order to provide a thorough understanding ofthe embodiments. However, it will be apparent to one skilled in the artthat these specific details are not required.

The above-described embodiments are intended to be examples only.Alterations, modifications and variations can be effected to theparticular embodiments by those of skill in the art without departingfrom the scope.

1. A method of processing a bituminous feed, the method comprising: a)solvent extracting the bituminous feed and forming a bitumen-rich streamand a bitumen-lean stream; b) recovering solvent from the bitumen-richstream to form a bitumen product; c) recovering solvent and water fromthe bitumen-lean stream to form dry tailings with a moisture content ofless than 40 wt. %; d) separating the dry tailings into at least twostreams, each stream of the at least two streams having a moisturecontent of less than 40 wt. %, based on at least one of a physicalproperty and a chemical property; and e) using at least one of the atleast two streams at an oil sands mine site.
 2. The method of claim 1,wherein the at least one of the physical property and the chemicalproperty comprises one of size, density, dipole moment, permeability,shape, magnetism, adhesiveness, wettability, attrition, strength,solubility, inductiveness, and electric charge.
 3. The method of claim1, wherein step d) comprises separating the dry tailings with aseparator, wherein the separator comprises one of a screen, a sieve, ablower, a cyclone, a centrifuge, a gravity settler, filtration,electrostatic precipitation, magnetism, a shaker, a grinder, milling,and rolling.
 4. The method of claim 1, wherein step d) comprisesseparating the dry tailings into a coarser particles stream havingcoarser particles and a finer particles stream having finer particles.5. The method of claim 4, further comprising adding water to the coarserparticles stream and pumping the coarser particles stream into place forconstruction of a mine form at the oil sands mine site, wherein the mineform comprises one of a dyke and a road.
 6. (canceled)
 7. The method ofclaim 4, wherein the finer particles stream is an impermeable layer atthe oil sands mine site.
 8. The method of claim 4, further comprisingdepositing the coarser particles stream over the finer particles streamto control dusting.
 9. The method of claim 1, wherein step e) comprisesdepositing the at least one of the at least two streams in an oil sandsmine pit.
 10. The method of claim 1, wherein step e) comprises using atleast one of the at least two streams for drainage, as foundation, forreclamation at the oil sands mine site.
 11. (canceled)
 12. The method ofclaim 1, further comprising, prior to step d), reducing a moisturecontent of the dry tailings by drying, extraction or agglomeration. 13.(canceled)
 14. The method of claim 1, further comprising mixing at leastone of the at least two streams with an additive comprising one of apolymer, gypsum, alum, and a resin.
 15. The method of claim 1, furthercomprising recovering at least one heavy metal from at least one of theat least two streams, wherein the heavy metals comprise at least one oftitanium, strontium, and vanadium.
 16. (canceled)
 17. The method ofclaim 1, further comprising grinding at least one of the at least twostreams.
 18. The method of claim 1, further comprising recycling atleast one of the at least two streams into the solvent extraction ofstep a).
 19. The method of claim 1, further comprising combining atleast one of the at least two streams with tailings generated from anaqueous-based bitumen extraction process.
 20. The method of claim 1,wherein the dry tailings have a water: solids mass ratio of less than0.15:1.
 21. The method of claim 1, wherein the oil sands mine site isone of a mine site employing aqueous-based bitumen extraction and a minesite employing solvent-based bitumen extraction.
 22. (canceled)
 23. Themethod of claim 1, wherein one of step a) comprises: contacting thebituminous feed with a bridging liquid comprising water, and anextraction liquor comprising a solvent; and separating water from thebitumen-rich stream; and agitation to form agglomerates comprisingsolids and water, wherein the agglomerates are in the bitumen-leanstream.
 24. (canceled)
 25. The method of claim 23, wherein at least 80wt. % of the agglomerates of step c) are less than 2 mm.
 26. The methodof claim 1, wherein the solvent comprises one of an organic solvent anda mixture of organic solvents.
 27. (canceled)